All three Democrats on the Senate’s Nominations Committee voted against the move; four Republicans voted in favor. A full Senate vote with a two-thirds majority is now needed to approve Warren’s appointment.

Gov. Greg Abbott appointed the billionaire CEO to the sought-after post 18 months ago. Warren has since been the subject of regular activism at the parks department, at his offices and at his home.

Energy Transfer Partners, based in Dallas, built the Trans-Pecos pipeline in West Texas and Dakota Access pipeline in North Dakota, both the focus of regular protests. Environmentalists argued the Trans-Pecos traversed pristine wilderness and the Dakota sacred Indian burial ground. They also worried the North Dakota pipeline, which cuts under the Missouri River, could spill and contaminate the river, the main water source for the Standing Rock Sioux reservation to the south.

More than 5,000 Texans have contacted their state Senator to oppose Warren’s nomination, the Sierra Club said.

“It’s disappointing that the majority on the committee would support a nominee with such inherent conflicts, but not surprising given the stranglehold the oil and gas industry has on the Texas Legislature,” said Cyrus Reed, Conservation Director of the Sierra Club’s Lone Star Chapter.

Warren said he is honored to have been appointed. “As a native Texan, he looks forward to continuing to serve on the Commission,” a spokeswoman said in a statement, “and to carry out its mission to manage our state’s natural and cultural resources.”